3 replies to this topic

[jdh]

Hello there. I'm a year 3 ChE student, studying at the National University of Singapore. I'm currently on industrial attachment with a petrochemical company's refinery and am working on a study for a Electrochlorinator used to generate hypochlorite from seawater to disinfect the water used in the cooling network. The chlorinator is usually on continous dosing with equivalent chlorine concentarion at 2ppm and interminent shock dosing every 8 hours. May need to redesign the unit for increased capacity.

Can i check if anyone knows what is the usual free chlorine residual for interminent shocking and for how long a period of time? I know the free chlorine residual for continous dosing is 0.5ppm, but i have answers ranging from 1ppm to 3 ppm for shock which will make a lot of difference in capacity.

Also, does anyone knows the current chlorine demand of seawater around Singapore and its associated islands? The basis for the original design was 1.5ppm i believe, but that was 25 years ago and i'm not sure if it changes. Pls advise

Or any reference to a source which i can check will do as well.

Thanks in advance!

[S.Chittibabu]

Mr JDH,

Normally for continous dosing is done at the rate of 1.5 to 2 ppm. Shock dosing is done for 15 to 20 minutes for every 8 hours. The rate will vary 3 to 5 ppm. The dosing will vary depending whether it is winter or summer. Summer season requires the maximum of 5 ppm. Having said the dosing quantity the demand have to calculated only on site measurement by observing the free chlorine present immediatly at the point of injection and at the point of discharge. It it has to be disposed safely into the sea then the dosing is adjusted in such a way not to exceed the free chlorine more than 0.1 ppm (in order to abide the local regulation of environmental body) at the point of discharge.

S.Chittibabu

[jdh]

Dear S.Chittibabu,

Thank you for your reply. Your input is appreciated. =)

I have also recently found a good book on electrochlorination background, theory and design "Conversion to On-Site Sodium Hypochlorite Generation--Water and Wastewater Applications" by L. Casson & J. Bess Jr (2003). I would recommend it to anyone who needs a reference on this topic in the future.

Regards
JDH

[jenand]

Dear S.Chittibabu,

Thank you for your reply. Your input is appreciated. =)

I have also recently found a good book on electrochlorination background, theory and design "Conversion to On-Site Sodium Hypochlorite Generation--Water and Wastewater Applications" by L. Casson & J. Bess Jr (2003). I would recommend it to anyone who needs a reference on this topic in the future.

Regards
JDH

Another good list of articles are as follows: http://www.water.sie...nt-default.aspx